In recent years, there have been developed a number of steam generators such as humidifiers, steam irons, steam inhalers, all of which have become popular in the market.
In particular, humidifiers and inhalers have been favorably noticed. Inhalers are effective as a measure for bronchitic or asthmatic patients, so that many related articles have been recently developed. However, most known inhalers are arranged such that 300-400 ml of water in a container is heated by means of an electric heater to generate steam and a saline solution or an adrenaline solution is sprayed entrained with the steam by application of a spraying principle using the pressure of the generated steam. For generators of this type, it takes approximately 7 minutes during the summer season and 10-15 minutes in the winter before steam is generated after introduction of water. Thus, most of the generators, in addition to requiring a relatively long time duration before steam generation, also involve difficulty in controlling the temperature of steam and no steam generation occurs unless a certain level of water is provided in spite of their use for a short time, and are poor in economy from a viewpoint of energy saving.
The humidifier is also becoming an important electric article in view of the growing demand for air conditioning coolers and the FF-type heating apparatus as a preventive measure against dryness of the air when using air conditioning coolers in the summer season or as a measure of humidification required when the FF type heaters are used in the winter season.
In principle, humidifiers are divided into two groups, ultrasonic and heating types. The heating type humidifier is scarcely employed since it requires a long time before steam is generated (as is the case with inhalers), resulting in poor economy from the standpoint of energy costs. On the other hand, the ultrasonic system is employed and since it generates water droplets (not steam) having a size of 5-30 .mu.m, it appears visually that steam generated simultaneously with the electric source being turned on; howwever, it actually takes a long time before the water droplets are vaporized into steam. In addition, fine water droplets (5-30 .mu.m) generated from the ultrasonic humidifier does not reach the lung by adsorption with organs, and thus the ultrasonic humidifier is not so favored from a standpoint of health. As a matter of course, there has been heretofore made an effort to improve ultrasonic generator elements in order to make finer the water droplets of the ultrasonic humidifier. To obtain finer water particles requires greater amounts of electric energy or involves greater levels of noise. As a consequence, the humidifiers which have been practically utilized from a view point of their commercial value are, in most cases, those in which the size of water droplets is in the range of 5-30 .mu.m, but such size was not satisfactory. That is, it is medically accepted that when taking into account an influence on human body, a particle size of below 1 .mu.m or a steam-like particle size is most ideal.